From: Hugh Hartwig <hhart...@be...> - 2009-01-26 16:43
>So there is a way to compile and link up to 64K. When I compile for the
>2618 it fails to link above 45K (3K for boot code) because of the location
>of .vectors. The linker file defines .fartext, but it doesn't seem to take
>advantage of this additional code space. Is there an attribute flag that
>will specify the location of code to this .fartext region?
The linker doesn't support sections with holes. Since the vectors are at
0x0ff80, the .text section can only extend to
0x0ff7f. Unfortunately the compiler automatically places everything into the
.text section.
you could place a function into the (for the linker defined) .fartext section
by using the __attribute__((section
(".fartext"))).
But calling these functions requires a CALLA command instead of the normal CALL
as well as a special return
command (polling a 32 bit instead of a 16 bit return address from stack). The
compiler won't generate them, so the
code cannot be executed in the .fartext section.
Without compiler support for the 430X command set, the .fartext section can
only be used for data. And accessing
the data must be done by a self-written assembly function using the 430X
commands for 20 bit access.
Also, since the compiler does not know about .fartext except that it is a
separate section of arbitrary location, it will
issue a section attribute error when you try to place code AND data into it by
using the __attribute__((section
(".fartext"))).
Anyway, if you have a big precalculated table (like a sinus table), you can
place it in .fartext and access it with your
own assembly code, freeing up a lot of the normal 64k area.
Better than nothing.
A good opportunity for designated math library or a printf_F function for
format text constants placed in .fartext
JMGross
